Soldiers are required to acquire, identify, and accurately fire on enemy targets at distances in excess of 100 meters and may use weapon-mounted sights. These sights may be mounted on small arms such as the M4A1 carbine and other weapons and are used to provide better target observation during day and night time missions. These sights may incorporate night vision or infrared technology or may be aligned with a device incorporating night vision or infrared technology.
Night vision devices are typically equipped with one or more image intensifier tubes to allow an operator to see visible wavelengths of radiation (approximately 400 nm to approximately 900 nm). They work by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that an operator can easily observe the image.
Devices with infrared sensors allow an operator to see people and objects because they emit thermal energy. Some of these devices operate by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this wavelength than cooler objects like trees or buildings. Since the primary source of infrared radiation is heat or thermal radiation, any object that has a temperature radiates in the infrared.
Fusion systems have been developed that combine image intensifiers with infrared sensors. The image intensification information and the infrared information may be fused together to provide a fused image that provides benefits over just image intensification or just thermal sensing.
A weapon-mounted housing may be used to hold the image intensifier tube or infrared sensor to a host weapon. The housing may provide protection from unintended contact or debris and may be coupled to a weapon with a suitable attachment mechanism, for example a rail grabber or other clamp.